Electric mat switch



March 22, 1960` c. FERRY ETAL ELECTRIC MAT swr'rcH 3 Sheets-Sheet 1Filed Oct. 2, 1958 r2 LI..

rNvENToRs tmE/.00N 5. ROBY CHAMBER/.A/N FERRY ATTORNEYS c. FERRY Erm.2,929,893 ELECTRIC MAT swITcH 3 Sheets-Sheet 2 March 22, 1960 Filed oct.2. 195e F IG. 5

IN VEN TCR3 SHEL DON 5. ROB Y CHAMBERLA/N FERRY BY M17 MW ATTORNEYSMarch 22, 1960 c. FERRY ETAL 2,929,893

' ELECTRIC MAT SWITCH Filed Oct. 2, 1958 3 Sheets-Sheet 3 FiG. 7

@lb 56a qa' j? Irl 1 Irl l IUT INVENTORS SHELDON S. ROB CHAMBERLA/N F RYTTORNEYS United States Patent ELECI'RIC MAT SWITCH Application October2, 1958, Serial No. 764,792

12 Claims. (Cl. 200-86) This invention relates to mat switches forcontrolling the operation of electrically actuated doors or the like inresponse to pressures such as those applied to the mat by personsstepping thereon.

A major object of the present invention is to provide an improvedelectric mat switch having a uniform sensitivity to pressures applied tovany point within an area comprising a major portion of its surface.

Another object is to provide an improved electric mat switch which iseconomical to construct and assemble and which lends itself to massproduction techniques.

Another object is to provide a mat switch of the multiple plate type soconstructed and arranged that the contact-making pressure is applied toa plate which is substantially nontiexible as to localized areas butwhich is mounted to transfer downward forces to a iiexible plate in amanner to insure positive circuit-making contact between noniiexible andflexible plates.

Another object is to improve and simplify the spacing elements employedbetween the contact-making plates of switches of the character describedwhich may be fabricatedat a low cost.

Other objects will be in part obvious and in part pointed out more indetail hereinafter.

The invention accordingly consists in the features of construction,combination of elements and arrangement of parts which will beexemplified in the construction hereafter set forth and the scope of theapplication of which will be indicated in the appended claims.

In the drawings:

Fig. 1 is a fragmentary view in vertical section showing a carpetcontact switch assembly incorporating the present invention with nopressure applied thereto and the contacts in open position.

Fig. 2A is a view showing the device of Fig. l under pressure such as isapplied by a person walking thereon, with the contacts in closedposition.

Fig. 3 `is a similar view of a carpet contact switch assembly showing analternate embodiment of the invention.

Fig. 4 is a view showing the device of Fig. 3 under pressure such as isapplied by a person walking thereon, with the contacts in closedposition.

Fig. k5 is a top plan view of a carpet contact switch assembly withportions broken away to disclose the assembly of plates and spacers.

Fig. 6 is a fragmentary perspective view exploded to illustrate thespacer and plate assembly of the device of Fig. 5. v

Fig. 7 is a top plan view of the carpet switch assembly of Fig. 3 withportions broken away to disclose the assembly of plates and spacers. f

Fig. 8 is a fragmentary perspective view exploded to illustrate thespacer and plate assembly of the device of Fig. 7.

Referring to Fig. l, a mat switch constructed in accordance with thepresent invention includes a pair of metal plates 12 and 14 normallymaintained in parallel ice spaced-apart relation by spacers or stencils16, with the plate assembly enveloped in a resilient housing-like mat 18internally chambered throughout a major portion thereof to receive thepaired plates between a top wall portion 2t) and a bottom wall portion22, mat 18 being constructed in a manner that the top and bottom wallsare normally in spaced parallel relation as shown in Fig. l. The bottomwall 22 of mat 18 is provided with integral supporting ribs 24 tomaintain a major portion of that wall spaced above a supporting surfacesuch as a floor 26, illustrated dotted, when the switch is not underpressure. The ribs 24 are disposed in staggered relationship withrespect to the spacers 16 and form supports for sheet 14 which areoffset relative to the spacers 16.

As shown in Figs. l and 2, the upper contact plate 12 is of heavy metalsheet stock which resists exing under the weight of a person steppingonto upper wall 2t), while lower contact plate 14 is of relatively lightmetallic sheet stock which readily lieXes under that weight. While theremay be slight over-all flexing of plate 12, such flexing as may occur isnot of a localized nature, nor does it materially contribute to theoperation of the switch. Plate 12 does however move downwardly as a unitunder the weight of a person stepping on resilient mat 18, but suchdownward movement is due to compression of the mat, mat 1S being of adeformable electrically insulating material such as plastic or rubbermaterial or the like. y

Operation of the switch shown in Figs. l and 2 is as follows: Pressureapplied to top wall 20 is transferred to top plate 12 which rests onspacers 16 which are in turn supported on the relatively iiexible plate14 which, in turn, is supported on the upper surface of the lower wall22. Spacers 16 are of an electrical insulating material which does notcompress appreciably under the weights involved, hence, due to therigidity of upper plate 12 which prohibits any appreciable iiexingbetween the spacers, the downward forces are transferred to lower plate14 solely through spacers 16. it will be seen that the spacers 16 arelaterally offset from the supporting ribs 24 of the lower mat wall 22.Preferably, all but those spacers closest the margins of the mat arepositioned midway between the ribs 24. The marginal spacers are atpositions inwardly of the supporting ribs at kthe mat margin and above aportion of lower wall 22 which is normally spaced above supportingsurface 26. Electrical terminals 25, 27 which are connected to theplates 1 2 and 14, respectively, lead to the edge of the mat forconnection to an electrical door operator circuit.

The weight of a person stepping on any portion of the upper mat surfaceinwardly of marginally reduced portions 28 results in downward forcesapplied to at least one, and in most instances to two or more of thespacers 16 to iiex downwardly one or more of the local areas of lowerplate 14 on which the spacers rest. Since localized areas of plate 14 soiiexed are in turn supported on correspondingareas of the flexible lowermat wall 22, which is spaced by ribs 24 above the oor, those areas ofthe lower plate are thus resiliently mounted, hence they readily tieXdownwardly under such applied forces, as shown in Fig. 2. However, sincethe areas of lower plate 14 directly above the supporting ribs 24 arenot free to tieX in the above manner, corresponding areas of upper plate12 are moved into firm circuit closing engagement therewith as the matis compressed under a weight above a predetermined minimum. The switchis designed to operate under a predetermined weight selected in view ofits intended use. Spacers 16 are separated at distances which insurepositive contact, hence a good electrical connection, between the upperand lower metallic plates, in response to applied pressures at anyposition throughout the mat surface inwardly of the relatively narrowmarginal portion 28.

A stencil or spacer construction particularly useful in this inventionis illustrated in Figs. 4 and 5. Fabrication costs'are reduced byemploying a single stencil 30 formed of a sheet of good electricalinsulating material such as cardboard, plastic, or the like, withrectangular or other shaped portions cut therefrom to define, forexample, a plurality of transverse spacers 32 which correspond tospacers i6 above described in respect to the structure of Figs. l and 2.The resulting mat switch, as shown in Fig. 4, closely resembles theconstruction illustrated in Figs. l and 2, a resilient mat 34 beingbroken away to show a heavy upper plate 36, spacer element 30,'a lowerflexible plate 3S viewable through the apertures of element 3f), and aplurality of supporting ribs 4t), shown dotted, and preferably providedin the manner above described as integral extensions of the lower matwall, not shown. Marginal strips 42, on each side of'spacer element 30,are positioned in abutment with integral marginal ribs 44 of mat 34which correspond to the marginally reduced areas 2S of the structure ofFigs. l and 2. Mat 34 is preferably constructed of a plastic material. e

The-'stencil and support structure for the lower flexibleplate can,ofcourse, take other form. For example, as seen in Figs. 3, 4, 7, and 8,stencil 50; is provided with a plurality of closely spaced relativelylarge circular apertures 51 and is positioned between substantiallyrigid upper plate 52 and'exible lower plate 53. A resilient upper mat 54and a resilient bottom wall 55 are provided in a similar manner as withthe embodiment described in Figs. 1 and 2. Bottom wall 5 supportsflexible plate 53 and is provided with a plurality of spaced raisedportions or button-like projections 56 which engage the supporting floorsurface, thereby to support the mat switch. As most clearly seen in Fig.7, wherein portions'of top plate 52 and upper carpet surface 54 havebeen broken away, raised portions 56 are generally circular in lateralcross-section and extend from a portion of maximum height or verticalcross-section 56a (shown dotted) to a portion of minimum height orvertical crosssection 56h (shown dotted) and are arranged so that thepoint 56a of maximum height is vertically aligned and substantiallyconcentric with apertures 51 in spacer 50.

Thus, as a downward force is exerted on substantially rigid top plate 52by a person walking on upper carpet surface 54, spacer 50movesodownwardly with plate 52 to deform lower support 55 so as to bringlower support portion 56b into contact with the supporting surface andthereby deform flexible lower plate 53 into engagement with upper plate52 in the region of maximum crosssection 56a of buttons 56. Thisengagement establishes electrical contact betweenplates 52 and 53 toclose an external electrical circuit between the terminals 60 and 61which are electrically connected to lower plate 53 and upper plate 52respectively.

extreme margins, is subject to the minimum predeter-V mined actuatingpressure.

' prising a rigid top plate, means supporting said top plate AsA will beapparent to persons skilled in the art, various modifications andadaptations of the structure above described will become'readilyapparent without departure from theV spirit and scope of the invention,the scope of which is defined in the appended claims@ VWe claim:

1. In an electric mat switch, the combination comfor downward movementas a unit, a flexible second plate,`

spacing means interposed between said top plate and said second plate,said spacing means defining a plurality of open areas where saidflexible second plate can be deformed into contact with said rigid topplate, and support means for said secondoplate, said support meanshaving a .varying cross-sectionwith a plurality of raised portionspositionedin Vertical alignment with said open areas whereby depressionof said top plate causes "de- Yformation of said second flexible platein the region of the raised Vportions of'said support means and intoengagement with said top plate.

2. ln an electric mat switch, the combination comprising a rigid topplate, means supporting said top plate for downward movement as a unit,a flexible second plate, spacing means disposed between said top plateand'said second plate and engageable with said top plate and said secondplate at spaced intervals, and means supporting said flexible secondplate at spaced intervals, the points at which said last named meanssupport said flexible second plate occurring intermediate the points atwhich said spacing means is engageable with said top plate and saidllexible second plate. A

3. In an electric mat switch, Ythe combination comprising a rigid topplate, means supporting said top plate for downward movement as a unit,a flexible second'plate, a

spacer between said top plate and said second plate, saidY spacer havingVa plurality of apertures formed therein, and a support for said secondplate, saidrsupport having a plurality of raised buttons thereon,saidbuttons being vertically aligned with the apertures Vin said spacer.

4. In an electric mat switch, the combination comprising a rigid topplate, means supporting said top plate for downward movement as a unit,a flexible second plate, a spacer interposed betweenV and engaging saidVtop plate and said second plate, said spacer having a plurality ofapertures formed therein, and a ilexible support for said flexiblesecond plate, said flexible support engaging said flexible second platethroughoutjone surface thereof and vhaving a plurality of dependingbuttons formed thereon,

said buttons being Vin verticalvalignment with the apertures in saidspacer. Y 1 Y 5. In an electric mat switch, a rigid top plate movabledownwardly as a unit, a flexible second plate parallel to the rigid topplate, a plurality of separated non-compressible spacers between therigid top plate and the flexible second plate, and a plurality of spacedsupports for the lexible plate disposed in staggered relationship withrespectV to Vsaid. spacers. Y

6. In a device of the character described, a resilient mat havingembedded therein parallel to the major plane thereof a rigid metalplate, a exible metal plate, a plu- Y Vllexible metal plate,electrically insulating spacersY dis- Vposed at intervals between saidplates to maintain them in substantially parallel spaced relation, and aresilient electrically insulating mat enclosing said plates andmaintaining them engaged withl said spacers, said mat having a contouredlower wall of varying cross section supporting said flexiblemetal plateand permitting deformation of said flexible metal plate in the regionsbetween said spacers by forces acting through said rigid plate and saidprovided with spaced depending portions engageable with a supportingsurface, a flexible metallic plate on the lower wall of said chamber,electrically insulating spacers disposed at intervals on said llexibleplate in staggered relationship to said depending portions, and arelatively nonexible metallic plate supported on said spacers in spacedrelation above said flexible plate. t

9. In a switch of the floor mat type, an upper relatively heavy metalplate which resists flexing under switch actuating pressures and a lowerrelatively light plate which flexes under said pressures, spaced apartseparators of non-conducting material intermediate said plates tonormally maintain the plates in parallel spaced relation, and spacedapart supporting means intermediate said spacers and below said lowerplate for contact with a supporting surface, whereby switch actuatingpressures applied to said upper plate are transmitted through saidseparators to non-supported areas of said lower plate to cause ilexurethereof and circuit closing contact between said plates in portionsintermediate said separators.

10. ln a switch of the door mat type including relatively heavy upperand lower spaced metal plates which resist exing under switch closingpressures and a relatively tliin metal plate which ilexes under suchpressures positioned in parallel spaced relation therebetween, spacedapart upper separators of non-conducting material between said upper andintermediate plates, and spaced apart lower separators between saidlower and intermediate plates, said lower separators being positionedsubstantially midway between said upper separators, whereby applicationof pressure to said upper plate causes said upper separators to ex saidlight plate to etect switch closing contact between the portions of saidheavy upper plate and said thin metal plate disposed above the lowerseparators.

1l. A switch of the oor mat type for controlling door actuatingmechanisms and the like comprising two superposed generally parallelimperforate sheet metal plates, the upper plate being suiciently rigidto resist flexing responsive to predetermined operating pressures andthe lower plate being sufficiently flexible to be deformed under thosepressures, means normally separating the plates in said parallelrelation comprising a plurality of spacedapart non-conducting andsubstantially non-compressible elements disposed intermediate theplates, and means resiliently mounting said lower plate in the area ofsaid spacers to permit operating pressures applied to said upper plateto move said upper plate as a unit toward said lower plate and causesaid spacers to deform portions ot said lower plate and permit switchclosing contact between the upper and lower plates in areas of saidlower plates not deformed by said spacers.

12. In a device of the character described, a mat of resilientelectrically insulating material provided with an internal chamberextending parallel to the major plane of the mat, a rigid metal plate, aflexible metal plate, said plates being disposed in said chamber, aplurality of electrically insulating and relatively non-compressibleelements positioned at intervals intermediate said plates to normallymaintain the plates in substantially parallel spaced relation with therigid plate adjacent the upper wall ot the chamber and the flexibleplate adjacent the lower chamber wall, the bottom of said mat beingcontoured to support portions thereof in the area of said insulatingelements above a supporting surface to permit iiexing of correspondingareas of said flexible plate by pressure applied to said rigid plate andtransmitted to said ilexible plate through said insulating elements.

References Cited in the le of this patent UNITED STATES PATENTS2,611,049 Roby Sept. 16, 1952

